In a harness circuit, it is often required to provide one or more branch electric wires from a main electric wire. Heretofore, there have been widely proposed two joint methods, i.e. a splice joint method in which a part of an electrically insulating sheath of the main electric wire is removed and one or more branch electric wires are connected by clamping them to an exposed core conductor of the main electric wire, and a joint connector method in which a circuit branch connector is arranged at a terminal of the main electric wire and conventional connectors having clamp terminals connected to the main wire and branch wires are inserted into the circuit branch connecter to constitute the branch circuit. The later method is disclosed in a Japanese Patent Document 1 mentioned later.
In the splice joint method, electric wires have to be connected to the main electric wire in such a manner that a group of one to three branch wires is connected by clamping, and therefore after connecting the branch wires, the harness is difficult to be handled. Moreover, the joint work could not be carried out on a manufacturing line, and therefore the splice joint method is not suitably applied to the line production.
The joint connector method has been developed to overcome the above mentioned drawbacks of the splice joint method. In the joint connector method, the joint connection can be performed on a harness manufacturing line, and therefore a production efficiency is superior to the splice joint method and a design change of harness circuit can be easily effected. However, the number of parts such as connectors, cooperating conventional connectors, bus bars, connection terminals and so on is increased, and thus a relatively longer time period is required for assembling harness circuits.
In particular, the known joint connector methods disclosed in the Japanese Patent Document 1 still contains various problems to be solved. For instance, space saving of the harness circuit, improvement in workability, simplification of harness circuit structure and improvement in an electric current capability are required. Furthermore, upon forming the branch circuits, the branch connection member is liable to be damaged and an electrical insulation could not be easily obtained.
In order to avoid the above mentioned damage for keeping the good electrical insulation, a Japanese Patent Document 2 has proposed a protection method and a jig using a thermal shrinkage tube. However, this protection method requires a heat source, and therefore an installation is liable to be large and the workability is not good.